Electrostate graphic development of encapsulated materials

ABSTRACT

A toner in which at least a major portion of the resin component is a soft polymer encapsulated and dispersed in a tough polymer matrix in a plurality of discrete domains, instead of as a single core. A convenient method of providing such dispersion is by the use of a block, graft or shaded copolymer, as a dispersing agent, comprised of components which are identical to the soft and tough polymers. The toner is pressure fixable.

This invention relates to electrostatography, and more particularly toimproved electrostatographic developing materials and the use thereof.

Electrostatography is best exemplified by electrophotography. The basicelectrophotographic process, as taught by C. F. Carlson in U.S. Pat. No.2,297,691, involves placing a uniform electrostatic charge on aphotoconductive insulating layer, exposing the layer to alight-and-shadow image to dissipate the charge on the areas of the layerexposed to the light and developing the resulting latent electrostaticimage by depositing on the image a finely divided electroscopic materialreferred to in the art as "toner". The toner will normally be attractedto those areas of the layer which retain a charge, thereby forming atoner image corresponding to the latent electrostatic image. This powderimage may then be transferred to a support surface such as paper. Thetransferred image may subsequently be permanently affixed to the supportsurface as by heat. Instead of latent image formation by uniformlycharging the photoconductive layer and then exposing the layer to alight-and-shadow image, one may form the latent image by directlycharging the layer in image configuration. The powder image may be fixedto the photoconductive layer if elimination of the powder image transferstep is desired. Other suitable fixing means such as solvent orovercoating treatment may be substituted for the foregoing heat fixingsteps.

The toners employed in the art are generally fixed to a support mediumby the application of heat and, therefore, such toners must be heated toa temperature at which the toner flows in order to effect fusing of thetoner to the support medium. The fusion technique, although highlysuccessful, has some disadvantages; namely, such a technique has notbeen readily adaptable to high speed machines as a result of the time orenergy required to raise the temperature of the toner to a temperatureat which the toner can be fused to the support medium. Attempts torapidly fuse a high melting point toner by means of oversized highcapacity heating units result in excessive energy requirements as wellas the problems associated with preventing the charring of paperreceiving sheets and of adequately dissipating the heat evolved from thefusing unit or units. Thus, in order to avoid charring or combustion,additional equipment such as complex and expensive cooling units arenecessary to properly dispose of the large quantity of heat generated bythe fuser. Incomplete heat removal can cause damage to heat sensitivemachine components. Further, the increased space occupied by and thehigh operating cost of the heating and cooling units, often outweigh theadvantages achieved by the increased machine speed. On the other hand,low molecular weight resins which are easily heat fused at relativelylow temperatures are often undesirable because these materials tend toform thick films on reusable photoconductor surfaces. These films tendto cause image degradation and contribute to machine maintenance downtime. In addition, low molecular weight resins tend to form tacky imageson the copy sheet which often offsets to other adjacent sheets. Further,toner particles containing low molecular weight resins tend to bridge,cake and block in the shipping container as well as in theelectrostatographic machine. Furthermore, many of such polymers do notpossess the toughness required to resist the mechanical attrition whichtends to break down the toner particles into undesirable dust fines.

An object of this invention is to provide an improvedelectrostatographic developer.

Another object of this invention is to provide a toner which overcomesthe above-mentioned deficiencies.

A further object of this invention is to provide a toner which iscapable of being rapidly and facilely fixed to a support surface.

These and other objects of the invention should be apparent from readingthe following detailed description thereof.

The objects of the present invention are broadly accomplished byproviding an electrostatographic toner of the colored resinous materialin which at least a major portion of the resinous material is aheterogeneous (two phase) physical mixture comprised of at least onesoft deformable polymer dispersed and encapsulated in a matrix of atleast one tough polymer, as a plurality of discrete domains, instead ofas a single core.

More particularly, the resinous portion of the toner includes twoincompatible polymers one of which is employed as a matrix and the otherof which is dispersed in a plurality of discrete domains andencapsulated in the matrix. The matrix component is a tough material toprovide the physical properties which prevents blocking of and providesstructural rigidity to the toner, and the dispersed component, is a softmaterial which provides the desired fixing properties. In the use ofsuch a two phase resin system, it has been found that the softermaterial must be completely encapsulated within the tough matrixmaterial, and in addition, it has been found that the manner in whichthe softer component(s) is dispersed within the matrix influences theproperties of the toner. The dispersion of the encapsulated softercomponent(s) as a plurality of domains of controlled size, results in animproved toner; in particular, a toner which is capable of being fixedby the application of pressure.

In general, the tough polymer which is employed as a matrix has a glasstransition temperature (Tg) of greater than about 50°C., preferably fromabout 55° to about 180°C., and more preferably from about 60° to about90°C. If the polymer is crystalline, then the melting temperature (Tm)is greater than about 40°C., preferably from about 50° to about 90°C andmore preferably from about 60° to about 70°C. Thus, if the tough polymeris crystalline, the Tm must be greater than about 40°C. The molecularweight (number average) of the tough polymer block is greater than 1500,generally from about 5,000 to about 300,000, and preferably from about10,000 to about 100,000.

The molecular weight and Tg of the tough polymer matrix is selected toprovide a matrix which is sufficiently tough to withstand the forcesinvolved in the development and which can also be deformed during thefixing step. If the tough polymer includes polar groups, the molecularweight can be lower than those polymers which do not include polargroups while still providing the requisite toughness. The propertieswhich are conveniently utilized in characterizing the tough polymer arethe properties of tensile strength, impact strength and modulus ofelasticity. In general, the tough polymer has a tensile strength of atleast about 3,000 psi, and more generally greater than about 5,000 psi,with the tensile strength generally not exceeding about 10,000 psi. Itis to be understood, however, that polymers with tensile strengths inexcess of about 10,000 psi could also be suitable for the purposes ofthe present invention. The tough polymer is also generally characterizedby an izod impact strength (ASTM Test Method D-256) of greater than0.25, more generally from about 0.25 to about 15, with most of the toughpolymers which are utilized in accordance with the invention having anizod impact strength of from about 0.25 to about 1.5. The tough polymeris also generally characterized by a modulus of elasticity (TensileModulus) of greater than 200,000 psi, and more generally greater than400,000 psi. The tough polymer used in accordance with the teachings ofthe present invention generally do not have a modulus of elasticity inexcess of 600,000 psi, but it is to be understood that tough polymershaving a modulus of elasticity greater than 600,000 psi are within thescope of the invention.

The tough polymer may be a homopolymer or a copolymer and asrepresentative examples of such polymers (the term polymer as usedherein includes homopolymers and copolymer, with the term copolymerreferring to polymers formed from two or more monomeric components),there may be mentioned: styrene polymers such as polystyrene, poly(halostyrene), poly (alkyl styrenes), styrene-n-butyl methacrylatecopolymer; polymers of alkylmethacrylates wherein the alkyl group hasfrom 1-3 carbon atoms; polymers of acrylonitrile; polymers of vinylhalides, such as vinyl chloride polymers; polyamides; polyesters;polymers of acrylic acid; polymers of methacrylic acid; polymers ofvinyl N-alkyl pyridine; polycarbonates and the like.

In general, the soft polymer, which can be amorphous or crystalline, hasa glass transition temperature (Tg) of less than about 30°C., preferablyfrom about -50° to about 10°C, and more preferably from about -50° toabout 0°C. The molecular weight (number average) of the soft polymer isgenerally from about 500 to about 50,000, and preferably from about1,000 to about 20,000. It is to be understood that within the specifiedranges, soft polymers with lower glass transition temperatures may havehigher molecular weights and still impart the desired fixing properties.

The molecular weight and glass transition temperature of the softpolymer are selected to provide a soft polymer core which issufficiently soft to deform upon the application of shear stress. Ingeneral, the soft polymers which are suitable for the purposes of thepresent invention are characterized by their yield stress, with theyield stress of the soft polymer generally being from about 20 to about20,000 psi, and preferably from about 50 to about 3,000 psi.

The soft polymer may be a homopolymer or a copolymer including random,block and alternating copolymers and as representative examples of suchpolymers (the term polymer as used herein includes homopolymers andcopolymers with the term copolymer referring to polymers formed of twoor more monomeric components), there may be mentioned: polymers ofalkylene oxides, such as polymers of ethylene oxide; polymers oflactones, such as polycaprolactone; siloxane polymers, such as poly(dimethylsiloxane); polymers of alkyl acrylates wherein the alkyl grouphas from 1-12 carbon atoms; polymers of alkyl methacrylates wherein thealkyl group has from 4-12 carbon atoms; urethane polymers; uncrosslinkeddiene polymers; polyolefin waxes; polymers of vinylidene chloride;polyesters such as the polyalkylene adipates, polyalkylene sebecates,vinyl acetate polymers, and the like.

The domain size of the soft polymer component, encapsulated within thematrix, has been found to influence both the fixing properties and theimpaction properties of the toner, with an increase in the domain sizeenhancing the pressure fixability of the toner and derogating from theimpaction properties thereof. In general, the average domain size of thesoft polymer component dispersed in the matrix is less than 15 microns;more generally from about 0.002 micron to about 8 microns, andpreferably from about 0.1 micron to about 2 microns. The domain size ofthe soft component encapsulated within the matrix may be determined byany of a wide variety of procedures known in the art; e.g., transmissionelectron microscopy of ultra thin microtomed sections; light scatteringtechniques; etc.

The soft polymer component and the tough polymer component areincompatible with each other; i.e., the soft and tough polymercomponents are not completely soluble in each other and form twodistinct phases, and may be employed over a wide range of proportions,provided that the tough polymer component is present in an amountsufficient to provide a protective matrix which essentially completelysurrounds the dispersed soft polymer component. In general, the matrixcomponent should be present in an amount from about 10% to about 90%, byweight, and preferably from about 50% to about 80%, by weight, based onthe two components.

The soft polymer component may be dispersed in the tough polymer matrixin a plurality of discrete domains by partially compatibilizing the softpolymer component with the tough polymer component. This may be easilyaccomplished by the use of a dispersing agent which is either a blockcopolymer comprised of one block compatible with the dispersed componentand a second block compatible with the matrix component and/or a graftcopolymer comprised of a polymer backbone compatible with one of thedispersed or matrix components and a polymer side chain compatible withthe other of said dispersed or matrix components and/or a shadedcopolymer formed of one component which is compatible with the matrixcomponent and a second component which is compatible with the dispersedcomponent (a shaded copolymer, as known in the art, is a randomcopolymer in which one end of the chain has a high concentration of onecomponent of the copolymer and the other end of the chain has a highconcentration of a second component of the copolymer. As a result ofsuch a structure a shaded copolymer functions as a dispersing agent forthe purpose of the present invention). In general, such compatibility isbest achieved by having one component of the block and/or graft and/orshaded copolymer identical to the dispersed soft component and a secondcomponent thereof identical to the tough matrix component. Thus, forexample, if the matrix component is polystyrene and the soft componentis polyethylene oxide, the dispersing agent would include polymericcomponents of ethylene oxide and styrene.

The amount of dispersing agent employed in the toner affects the domainsize of the dispersed soft component, with an increase in the amount ofthe dispersing agent decreasing the domain size, as a result ofproviding an increase in the amount of interface sites. The amount ofdispersing agent is controlled to provide domain sizes in the order ofthose hereinabove specified. In general, the amount of dispersing agentemployed is from about 1% to about 50%, and preferably from about 5% toabout 20%, by weight, of the three components. In addition, themolecular weight of each of the components of the dispersing agentpreferably corresponds to or is less than the molecular weight of thecorresponding tough and/or soft polymer component of the toner.

The block and/or graft and/or shaded copolymer used as a dispersingagent may include polymeric components in addition to those present asthe dispersed and matrix phases of the toner, and preferably the blockand/or graft copolymer is comprised of only those polymeric componentspresent in the toner. If one of the components of the toner is acopolymer, then one of the blocks and/or components of the graft ispreferably also a copolymer, but in general, the toner components arehomopolymers and, therefore, the block and/or graft copolymer is alsocomprised of homopolymeric units.

The block copolymers and graft copolymers and shaded copolymers used asdispersing agents are known in the art and may be prepared by any one ofa wide variety of well-known procedures. The manner of producing suchblock and/or graft copolymers and/or shaded copolymers does not form anypart of the present invention and, accordingly, no further descriptionis deemed necessary for a full understanding of the present invention.

Another manner of partially compatabilizing the dispersed soft polymerwith the tough polymer matrix to provide a plurality of discretedomains, instead of a single core, of the soft polymer dispersed in thetough polymer matrix is by using a block and/or graph copolymer as oneor both of the dispersed and matrix components. Thus, for example, thedispersed soft polymer component may be comprised of a block or graftcopolymer, one component of which is a soft polymer, as hereinabovedescribed, and the other component of which is compatible with the toughpolymer matrix, with the aforementioned other component functioning as adispersing agent for dispersing the soft polymer component as aplurality of discrete domains in the tough polymer matrix. Similarly,the tough polymer matrix may be comprised of a block or graft copolymer,one component of which is a tough polymer, as hereinabove described, andthe other component of which is compatible with the dispersed softpolymer, with the aforementioned other component functioning as adispersing agent for dispersing the soft polymer component as aplurality of discrete domains in the tough polymer matrix. Thus, forexample, a block copolymer of styrene and butadiene may be used as thesoft polymer component and a polystyrene used as the matrix component,with the styrene component of the block copolymer functioning as adispersing agent to disperse the butadiene component of the blockcopolymer as a plurality of domains in the polystyrene matrix.

The resin mixture comprised of a soft polymer component encapsulated ina tough polymer component may be prepared by spray drying of the polymercomponents from a solvent comprised of a mutual solvent for allcomponents, and a preferential solvent for the matrix component, whichhas a boiling point greater than the mutual solvent. The spray dryingresults in an initial removal of the mutual solvent which precipitatesthe soft polymer component to form a matrix about the soft polymercomponent. Alternatively, a mutual solvent for all components in whichthe dispersed component is less soluble than the matrix component mayalso be employed for producing the encapsulated toner.

Specific techniques for producing encapsulated toner in accordance withthe present invention are also described in U.S. application Ser. No.214,374 now U.S. Pat. No. 3,784,052 and U.S. application Ser. No.214,031 now U.S. Pat. No. 3,830,750, both filed concurrently herewith,and the teachings of such applications in this respect are herebyincorporated by reference.

Another technique for producing toners in accordance with the presentinvention is coascervation. Coascervation generally involves dissolvingboth the dispersed and matrix component in a mutual solvent followed bythe addition of a non-solvent in a manner to precipitate both componentsfrom the solution, with the dispersed component being precipitated priorto the matrix component. Coascervation is known in the art and,accordingly, no further details are deemed necessary for anunderstanding of the application of this technique for producing theencapsulated toners of the present invention.

The toner of the present invention includes a colorant, either a pigmentor dye, in a quantity sufficient to impart color to the resincomposition, generally in a quantity up to about 25%, by weight, andparticularly from about 1% to about 20%, by weight of the toner, wherebythe resulting toner will form a clear visible image on a transfermember. Any one of a wide variety of pigments or dyes which do notadversely affect the properties of the toner may be employed to impartcolor to the resin; e.g., carbon black, a commercial red, blue or yellowdye, and since such dyes and/or pigments are well known in the art, nodetailed enumeration thereof is deemed necessary for a fullunderstanding of the invention. The toners of the present inventiongenerally have an average particle size of less than 30 microns andpreferably from about 10 to about 20 microns.

The hereinabove described toner of the invention may also include othermaterials generally employed for modifying the characteristics of atoner, such as conductive materials to modify the triboelectricproperties thereof or the like, and the use of such materials is deemedto be within the scope of those skilled in the art from the teachingsherein. Similarly, the toner may include a resinous component other thanthe hereinabove described resin mixture, provided that at least a majorportion of the resinous portion of the toner is comprised of thehereinabove described encapsulated resin mixture; generally, theencapsulated resin mixture comprises from about 80% to about 100%,preferably from 90% to 100%, of the resinous portion of the toner. Theremaining portion of the resinous component of the toner, if any, isgenerally a resin of the type employed to modify the physical propertiesof a toner material.

The toner hereinabove described, is employed in a developer compositionby loosely coating the toner on a suitable electrostatographic developercarrier surface to which the toner is affixed by electrostaticattraction, as generally known in the art. Thus, for example, the tonercomposition may be employed in the cascade development technique, asmore fully described in U.S. Pat. No. 2,618,551 to Walkup, U.S. Pat. No.2,618,552 to Wise, and U.S. Pat. No. 2,638,416 to Walkup et al. In thecascade development technique, the developer composition is produced bymixing toner composition with a carrier, either electrically conductingor insulating, magnetic or non-magnetic, provided that the carriermaterial when brought in close contact with the toner compositionacquires a charge having an opposite polarity to that of the tonerwhereby the toner adheres to and surrounds the carrier. Thus, thecarrier material is selected in accordance with its triboelectricproperties so that the toner is either above or below the carriermaterial in the triboelectric series, to provide a positively ornegatively charged toner.

The carrier particles are larger than the toner particles by at leastone order of magnitude of size and are shaped to roll across the latentimage-bearing surface. In general, the carrier particles should be ofsufficient size so that their gravitational or momentum force is greaterthan the force of attraction of the toner particles in the area of theimage-bearing surface where the toner particles are retained, wherebythe carrier will not be retained by the toner particles which areattracted to the image-bearing surface. The carrier particles generallyhave a particle size from about 30 to about 1000 microns, but it is tobe understood, that the carrier particles may be of a size other than asparticularly described, provided that the carrier flows easily over theimage-bearing surface, without requiring special means for effectingremoval of the carrier particles from the image-bearing surface.

The degree of contrast or other photographic qualities in the finishedimage may be varied by changing the relative proportions of toner andcarrier material and the choice of optimum proportions is deemed to bewithin the scope of those skilled in the art. In general, however, thetoner of the invention is employed in amounts to provide weight ratiosof carrier to toner of from about 25:1 to about 250:1, preferably fromabout 75:1 to about 100:1, to produce a dense readily transferableimage.

In addition to the use of particles to provide the carrier surface, thebristles of a fur brush may also be used. Here also, the toner particlesacquire an electrostatic charge of polarity determined by the relativeposition of the toner particles and the fur fibers in the triboelectricseries. The toner particles form a coating on the bristles of the furclinging thereto by reason of the electrostatic attraction between thetoner and the fur just as the toner clings to the surface of the carrierparticles. The general process of fur brush development is described ingreater detail in U.S. Pat. No. 3,251,706 to L. E. Walkup.

Even more closely related to the cascade carrier development is magneticbrush development. In this process, a carrier is selected havingferromagnetic properties and selected relative to the toner in atriboelectric series so as to impart the desired electrostatic polarityto the toner and carrier as in cascade carrier development. On insertinga magnet into such a mixture of toner and magnetic material the carrierparticles align themselves along the lines of force of the magnet toassume a brush-like array. The toner particles are electrostaticallycoated on the surface of the powder carrier particles. Developmentproceeds as in regular cascade carrier development on moving the magnetover the surface bearing the electrostatic image so that the "bristles"of the magnetic brush contact the electostatic image-bearing surface.

Still another method of carrier development is known as sheet carrierdevelopment in which the toner particles are placed on a sheet as ofpaper, plastic, or metal. This process is described in U.S. Pat. No.2,895,847 to C. R. Mayo. As described therein the electrostaticattraction between the sheet surface and toner particles necessary toassure electrostatic attraction therebetween may be obtained by leadingthe sheet through a mass of electroscopic toner particles whereby thereis obtained a rubbing or sliding contact between the sheet and thetoner. In general, it is desirable to spray the surface of the sheetbearing the electroscopic toner particles with ions of the desiredpolarity as by the use of a corona charging device as described in thepatent of Mayo.

The resulting image of toner particles of the image-bearing surface maythen be transferred to a suitable transfer member to form the finalcopy. The transfer of the toner particles may be effected adhesively orelectrostatically as known in the art.

The toner as should be apparent from the hereinabove teachings, may beemployed in a wide variety of developer compositions byelectrostatically coating the toner composition to a suitable carriersurface, which is subsequently passed over a latent image-bearingsurface. The toner of the invention may also be employed for developingan electrostatic latent image formed by other than electrophotographicmeans; for example, the development of electrostatic latent imagesformed by pulsing electrodes as employed in electrostatic printingprocesses. In addition, the toner of the invention may be employed fordeveloping an electrostatic latent image on a surface other than aphotoconductive insulating surface. Therefore, the overall invention isnot limited to a specific technique for forming or developing anelectrostatic latent image or to a specific carrier for the toner.

The toners of the present invention are capable of being fixed to asuitable support medium such as paper to provide a finished copy by theapplication of pressure; with the particular pressure required foreffecting such pressure fixing varying with the particular toneremployed. The pressure is preferably provided by pressing the transfermaterial having the toner image thereon between a pair of polished metalrollers that are in contact with each other under a specified pressure.In general, the roll loading is from about 10 to about 600 pounds perlinear inch, and preferably from about 50 to about 400 pounds per linearinch. The roll loading in pounds per linear inch is the total appliedforce divided by the length of the roll. In some cases, the pressurefixing of the toner to the support medium may be heat assisted; e.g., bythe use of a coated or uncoated heated metal roll and an uncoated orelastomeric coated backup roll.

It is to be understood, however, that although the toners of the presentinvention are particularly suitable for the preparation of a final copyby pressure fixing, such toners may also be fixed by conventionalprocedures; e.g., heat fusing.

This invention is further illustrated by the following examples but itis to be understood that the scope of the invention is not to be limitedthereby. Unless otherwise specified, all parts are by weight.

EXAMPLE I

The block copolymer poly (ε-caprolactone) - polystyrene - poly(ε-caprolactone) is prepared by coupling dicarboxy terminatedpolystyrene with poly (ε-caprolactone) having one terminal --OH group.The block is comprised of 60% polystyrene and 40%, all by weight, of thepolycaprolactone. The number average molecular weight of the blockcopolymer is 27,000.

A toner is prepared from 75:25 mixture of polystyrene having a molecularweight of 200,000 (DOW 678) and poly (ε-caprolactone) having a molecularweight of 2,000 and varying amounts of the above described copolymer byspray drying the mixture with MOGUL L carbon black using methyl isobutylketone as the solvent. The resulting toner has 5 wt.% of the carbonblack and an average particle size of about 15 microns.

A toner (A) prepared without any block copolymer is comprised of asingle core of polycaprolactone encapsulated in the polystyrene and

Toners (B & C) prepared with 10 wt.% and 20 wt.%, respectively, based onthe three components, of the block copolymer are comprised of aplurality of discrete domains of polycaprolactone, having an averagedomain size of 0.5 and 0.1 micron, respectively, (determined bytransmission electron microscopy).

The toner is combined with glass beads (250 micron) to produce adeveloper having 1 wt.% of the toner.

The developer is used to develop an electrostatic latent image bycascading the developer (three times) over an electrostatic latent imageformed on a flat selenium plate charged to +700 volts. The image istransferred to paper using +700 volts and fixed using 3 inch bare steelrollers at room temperature with the loading being 400 pounds per linearinch and the roller speed 4.2 inches/sec.

The final image which is prepared from toner A is smeared upon rubbingwith moderate pressure.

The final image which is prepared from toners B & C do not smear uponthe rubbing with moderate pressure. The toner B has better fixproperties than toner C, but toner C has a greater resistance toimpactation and block than toner B.

EXAMPLE II

5g of a styrene - butadiene block copolymer (KRATON 4113), 10g ofpolystyrene (PS-2) and 5g of a tackifying agent (PICCOTEX LTP-135) aredissolved in methyl ethyl ketone and hexane is added while stirring, toprovide 160 cc of methyl ethyl ketone and 240cc of hexane. 1g of MOGUL Lcarbon black is dispersed by ultrasonics in about 25cc of methyl ethylketone and the carbon black dispersion stirred into the polymersolution. The resulting mixture is spray dried to produce a toner havingan average particle size in the order of 15 microns.

The toner is combined with glass beads 250 micron) to produce adeveloper having 1 wt.% of the toner.

The developer is used to develop an electrostatic latent image bycascading the developer (three times) over an electrostatic latent imageformed on a flat selenium plate charged to +700 volts. The image istransferred to paper using +700 volts and fixed using 3 inch bare steelrollers at room temperature with the loading being 400 pounds per linearinch and the roller speed 4.2 inch/sec.

An acceptable fixed image is obtained.

EXAMPLE III

A 1:1 block copolymer having a weight average molecular weight of 13,000for each block of polyvinyl acetate and polystyrene is prepared bycoupling carboxy terminated vinyl acetate to polystyrene terminated withan acid chloride.

2.5 grams of poly (vinyl acetate) (M.W.: 7000), 7.5g of polystyrene (DOW678) and 1 gram of the polystyrene - poly (vinyl acetate) blockcopolymer are dissolved in toluene and combined with 0.5g of MOGUL Lcarbon black. The mixture is spray dried to produce toner having anaverage particle size in the order of 15 microns.

The toner is combined with glass beads (250 microns) to produce adeveloper having 1wt.% of the toner.

The developer is used to develop an electrostatic latent image bycascading the developer (three times) over an electrostatic latent imageformed on a flat selenium plate charged to +700 volts. The image istransferred to paper using +700 volts and fixed using 3 inch bare steelrollers (the upper roller is at a temperature of 120°F.), with theloading being 400 pounds per linear inch and the roller speed 4.2inch/sec.

EXAMPLE IV

A block copolymer of polyethylene oxide - polystyrene - polyethyleneoxide in which the number average molecular weight of polystyrene is10,500 and the number average molecular weight of each polyethyleneoxide block is 8400 is prepared by a two stage process as disclosed inthe article by O'Malley et al., "Synthesis and Thermal TransitionProperty of Styrene - Ethylene Oxide Copolymers", appearing in PolymerPreprints Vol. 10, No. 2, Pages 796-819 (September, 1969).

A 60:40 mixture of polyethylene oxide (CARBOWAX 1540) and polystyrene(DOW 678) is prepared and 10%, by weight, based on the three components,of the above block copolymer is added thereto.

A toner is prepared containing 5wt.% MOGUL L carbon black by spraydrying using a 1:1 mixture of chloroform and ethyl benzene as solvent.The toner has an average particle size of about 15 microns and thepolyethylene oxide is dispersed as a plurality of discrete domainshaving an average size of 0.6 - 0.7 micron.

The toner is combined with glass beads (250 micron) to produce adeveloper having 1 wt.% of the toner.

The developer is used to develop an electrostatic latent image bycascading the developer (three times) over an electrostatic latent imageformed on a flat selenium plate charged to +700 volts. The image istransferred to paper using +700 volts fixed using 3 inch bare steelrollers at room temperature with the loading being 400 pounds per linearinch and the roller speed 4.2 inch/sec.

An acceptable fixed image is obtained.

EXAMPLE V

A block copolymer of poly (dimethyl siloxane) - polystyrene - poly(dimethylsiloxane) is prepared by the procedure described by Morton etal, Journal of Applied Polymer Science, Vo. 8, 2707-2716 (1964). Theblock copolymer has a weight average molecular weight of 50,000.

A 75:25 mixture of polystyrene (DOW 678) and poly (dimethylsiloxane(M.W.:100,000) is prepared and 10%, by weight, based on the threecomponents, of the above block copolymer is added thereto.

A toner is prepared containing 5 wt.% MOGUL L carbon black by spraydrying using a 50:30 mixture of hexane and ethyl acetate as solvent. Thetoner has an average particle size of about 15 microns.

The toner is combined wth glass beads (250 micron) to produce adeveloper having 1 wt.% of the toner.

The developer is used to develop an electrostatic latent image bycascading the developer (three times) over an electrostatic latent imageformed on a flat selenium plate charged to +700 volts. The image istransferred to paper using +700 volts and fixed using 3 inch bare steelrollers at room temperature with the loading being 400 pounds per linearinch and the roller speed 4.2 inch/sec.

The fixed image is acceptable.

EXAMPLE VI

Isopropylidenediphenoxypropanol is reacted with adipic acid to provide apolyester having a weight average molecular weight of 2100.

The above polyester is coupled to acid chloride terminated polystyreneto produce a 1:1 block copolymer having a weight average molecularweight of 6000.

A 1:1 mixture of polystyrene (DOW 678) and the above polyester isprepared and 10%, by weight, based on the three components, of the aboveblock copolymer is added thereto.

A toner is prepared containing 5 wt.% MOGUL L carbon black by spraydrying using a 1:1 mixture of chloroform and heptane as solvent. Thetoner has an average particle size of about 15 microns.

The toner is combined with glass beads (250 micron) to produce adeveloper having 1 wt.% of the toner.

The developer is used to develop an electrostatic latent image bycascading the developer (three times) over an electrostatic latent imageformed on a flat selenium plate charged to +700 volts. The image istransferred to paper using +700 volts and fixed using 3 inch bare steelrollers at room temperature with the loading being 400 pounds per linearinch and the roller speed 4.2 inch/sec.

The fixed image is acceptable.

EXAMPLE VII

A 1:1 block copolymer having a weight average molecular weight of 50,000of bis-phenol A polycarbonate and poly (dimethyl siloxane) is preparedby the method described by Kambour, Block Polymers, p. 263, edited by S.L. Aggerwal, Plenum Press (1970).

A 1:1 mixture of polycarbonate (LEXAN 101) and poly (dimethyl siloxane)gum having a weight average molecular weight of 200,000 is prepared and10%, by weight, based on the three components, of the above blockcopolymer is added thereto.

A toner is prepared containing 5 wt.% MOGUL L carbon black by spraydrying using a 1:1 mixture of tetrahydrofuran and chloroform as solvent.The toner has an average particle size of about 15 microns.

The toner is combined with glass beads (250 micron) to produce adeveloper having 1 wt.% of the toner.

The developer is used to develop an electrostatic latent image bycascading the developer (three times) over an electrostatic latent imageformed on a flat selenium plate charged to +700 volts. The image istransferred to paper using +700 volts and fixed using 3 inch bare steelrollers at room temperature with the loading being 400 pounds per linearinch and the roller speed 4.2 inch/sec.

The fixed image is acceptable.

EXAMPLE VIII

A 1:1 block copolymer having a weight average molecular weight of 20,000is prepared by coupling carboxy terminated poly (hexamethylene sebecate)to polystyrene terminated with an acid chloride.

A 1:1 mixture of polystyrene (DOW 678) and poly (hexamethylene sebacate)having a weight average molecular weight of 7000 is prepared and 10% byweight, based on the three components, of the above block copolymer isadded thereto.

A toner is prepared containing 5 wt.% MOGUL L carbon black by spraydrying using a 1:1 mixture of chloroform and heptane as solvent. Thetoner has an average particle size of about 15 microns.

The toner is combined with glass beads (250 micron) to produce adeveloper having 1 wt.% of the toner.

The developer is used to develop an electrostatic latent image bycascading the developer (three times) over an electrostatic latent imageformed on a flat selenium plate charged to +700 volts. The image istransferred to paper using +700 volts and fixed using 3 inch bare steelrollers at room temperature with the loading being 400 pounds per linearinch and the roller speed 4.2 inch/sec.

The fixed image is acceptable.

EXAMPLE IX

A 75:25 mixture of polystyrene (DOW 678) and uncrosslinked polybutadiene(weight average molecular weight 200,000) is prepared and 10%, byweight, based on the three components, of a 1:1 linear graft copolymercomprised of uncrosslinked polybutadiene (weight average molecularweight: 200,000) and polystyrene (weight average molecular weight:10,000) is added thereto.

A toner is prepared containing 5 wt.% MOGUL L carbon black by spraydrying using a 1:1 mixture of chloroform and heptane as solvent. Thetoner has an average particle size of about 15 microns.

The toner is combined with glass beads (250 micron) to produce adeveloper having 1 wt.% of the toner.

The developer is used to develop an electrostatic latent image bycascading the developer (three times) over an electrostatic latent imageformed on a flat selenium plate charged to +700 volts. The image istransferred to paper using +700 volts and fixed using 3 inch bare steelrollers at room temperature with the loading being 400 pounds per linearinch and the roller speed 4.2 inch/sec.

The fixed image is acceptable.

EXAMPLE X

A 1:1 mixture of polyethylene oxide (CARBOWAX 1540) and polystyrene (DOW678) is prepared and 10%, by weight, based on the three components, ofthe block copolymer of Example IV is added thereto.

A toner is prepared containing 5 wt.% MOGUL L carbon black by spraydrying using a 1:1 mixture of chloroform and ethyl benzene as solvent.The toner has an average particle size of about 15 microns and thepolyethylene oxide is dispersed as a plurality of discrete domainshaving an average size of 0.5 micron.

The toner is combined with glass beads (250 micron) to produce adeveloper having 1 wt.% of the toner.

The developer is used to develop an electrostatic latent image bycascading the developer (three times) over an electrostatic latent imageformed on a flat selenium plate charged to +700 volts. The image istransferred to paper using +700 volts and fixed using 3 inch bare steelrollers at room temperature with the loading being 400 pounds per linearinch and the roller speed 4.2 inch/sec.

The fixed image is acceptable.

EXAMPLE XI

The block copolymer poly (ε-caprolactone) - random styrene -n-butylmethacrylate copolymer - poly (ε-caprolactone) is prepared by couplingthe dicarboxy terminated random copolymer with poly (ε-caprolactone)having one terminal --OH group. The block copolymer has a number averagemolecular weight of 30,000 and is comprised of about equal parts, byweight, of the polycaprolactone and the random copolymer.

A toner is prepared from a 75:25 mixture of a random copolymer ofstyrene and n-butyl methacrylate having a weight average molecularweight of 20,000, and poly (ε-caprolactone) having a weight averagemolecular weight of 2,000 by spray drying the mixture with MOGUL Lcarbon black using methyl isobutyl ketone as the solvent. The resultingtoner has 5 wt.% of the carbon black and an average particle size ofabout 15 microns.

The developer is used to develop an electrostatic latent image bycascading the developer (three times) over an electrostatic latent imageformed on a flat selenium plate charged to +700 volts. The image istransferred to paper using +700 volts and fixed using 3 inch bare steelrollers at room temperature with the loading being 400 pounds per linearinch and the roller speed 4.2 inch/sec.

The fixed image is acceptable.

The toners of the present invention are particularly advantageous inthat such toners are capable of being fixed to a support in imageconfiguration by the application of pressure, and in addition, possessthe structural properties required to withstand the forces encounteredin the development process. The ability to fix a toner image by theapplication of pressure is advantageous in that pressure fixing, withand without heat assistance, is capable of producing fixed images inshorter periods of time.

The encapsulated toners of the present invention are an improvement overencapsulated toners in which there is a single core in that the use of aplurality of discrete domains of soft polymer prevents gross failure andseparation of the soft polymer phase from the matrix. In addition, thetoner is more uniform thereby providing improved blocking properties.

Numerous modifications and variations of the present invention arepossible in light of the above teachings and, accordingly, within thescope of the appended claims of the invention may be practiced otherthan as particularly described.

What is claimed is:
 1. An electrostatographic toner comprising dryparticulate toner particles comprising a colorant selected from thegroup consisting of pigments and dyes, an electrophotographic resin,said resin comprising at least one soft deformable polymer encapsulatedin a matrix of at least one tough polymer, said soft polymer beingencapsulated in the tough polymer matrix in a plurality of discretedomains, said soft polymer being selected from the group consisting ofalkyl acrylate polymers in which the alkyl group has from 1-12 carbonatoms, alkylmethacrylate polymers in which the alkyl group has from 4-12carbon atoms, siloxane polymers, lactone polymers, vinyl acetatepolymers, alkylene oxide polymers, and unsaturated diene polymers, andsaid tough polymer being selected from the group consisting of styrenepolymers including polystyrene, poly halo styrene, poly alkyl styrenes,styrene-n-butylmethacrylate copolymers; polymers of alkyl-methacrylateswherein the alkyl group has from 1-3 carbon atoms; polymers ofacrylonitrile; polymers of vinyl halides, including vinyl chloridepolymers; polyamides, polyesters, polymers of acrylic acids; polymers ofmethacrylic acids, polymers of vinyl-N-alkyl pyridene; and polycarbonates.
 2. The toner composition as defined in claim 1 wherein theaverage domain size of the soft polymer component dispersed in thematrix is less than 15 microns.
 3. The toner composition as defined inclaim 1 wherein said matrix is present in a range of 10-90% by weight ofthe weight of both components.
 4. The toner as defined in claim 1further comprising a dry electrostatographic particulate carriermaterial.
 5. The toner as defined in claim 1 wherein said tough polymeris a crystalline polymer having a melting temperature of greater than40°C and said soft polymer is a crystalline polymer.
 6. Anelectrostatographic toner comprising dry particulate toner particlescomprising a colorant selected from the group consisting of dyes andpigments, and a finely-divided resin, said resin comprising at least onesoft deformable polymer encapsulated in a matrix of at least one toughpolymer, said soft polymer being encapsulated in the tough polymermatrix in a plurality of discrete domains, said tough polymer having aglass transition temperature (Tg) greater than 50°C, a molecular weightnumber average greater than 1,500, a tensile strength of at least 3,000psi, an Izod impact strength of greater than 0.25, and a modulus ofelasticity greater than 200,000 psi and said soft polymer having a glasstransition temperature (Tg) less than 30°C, a number average molecularweight of from 500-50,000, and a yield stress of from 20-20,000 psi. 7.The toner as defined in claim 5 wherein said tough polymer has a glasstransition temperature of from 60°-90°C, a molecular weight numberaverage of from 10,000-100,000, a tensile strength not exceeding 10,000,an Izod impact strength of from 0.25-1.5 and a modulus elasticity notexceeding 600,000 psi, and wherein said soft polymer has a glasstransition temperature (Tg) of from -5°-0°C, a number average molecularweight of from 1,000-20,000 and a yield stress of from 50-3,000 psi. 8.The toner as defined in claim 7 wherein the average domain size of asoft polymer component dispersed in the matrix is less than 15 microns.9. The toner as defined in claim 7 wherein the percentage of said matrixis 10-90% by weight of the mixture of the two components.
 10. The toneras defined in claim 7 wherein said tough polymer is selected from thegroup consisting of crystalline and amorphous polymers, said crystallinepolymers having a melting temperature of greater than 40°C and said softpolymer is selected from the group consisting of amorphous polymers andcrystalline polymers.
 11. The toner composition as defined in claim 7further comprising an electrostatographic dry particulate carriermaterial.